Buzzing gear lever

[Svenb]

I broke my elbow in my left and lost about 4 inches of reach so fitted a quickshift knuckle from Burton performance, ever since it buzzers like mad from 3.5k revs. I did poly bush the cradle at the same time but can't see it being that that's vibrating.
nothing is touching underneath either.
Could the small plastic bush on the bottom of the quickshift be to hard??
Seriously considering swapping it back to the standard one and possibly bending the lever instead.